#1934

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IMSAI Guy

Күн бұрын

Episode 1934
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Пікірлер: 18

@ludmilascoles1195 2 ай бұрын

One of the old guys at the radio club said he could tune any oscillator to 1004 by ear! When asked how he said easy, I did it for so long I am deaf to it😂 I just tune until I can't hear it

@rorymacleod8488 2 ай бұрын

I used one for 30 years, it was easilly the highest quality test set i ever used !!

@RideGasGas 2 ай бұрын

Impulse noise simulates things like lightning. In ye olde days you used to be able to hear static on phone calls when lightning was happening somewhere along the path. This feature is letting you check the clamping on the circuit to verify that impulse noise won't drive the audio volume to the rails when a noise spike is placed on the line.

@andymouse 2 ай бұрын

So cool ! Thanks.

@henrybecker2842 2 ай бұрын

WECO - Western Electric Co. WECO was one of the major manufacturing arms of the Bell System 😁

@davidv1289 2 ай бұрын

The receive section supplies the selected load, usually 600 ohms for Telco lines, unless the BRDG (bridge) button is pressed. In bridge the receiver presents a high impedance to the line. This is used when the end user equipment remains connected (terminates the line) while testing the line. The dial terminals allow a standard rotary dial to be connected for use on a 2 wire dial line. Impulse noise is a measurement performed by the receive section over a long time period - a minimum of 5 minutes on this unit. The use of 1004 Hz has to do with D1 Channel Bank equipment from the 60's - exact, continuous 1000 Hz tones would cause bit errors in the multiplexers. Regards, David

@typohits8213 2 ай бұрын

The TIA has a lage glossary of communications terms and concepts with brief explanations and cross-references online. This instrument defaults to DBrnC, or Dbm relative to noise with C message weighting. Telcos most often work with signals relative to the noise power on a circuit, rather than relative to some arbitrary reference level. This can sometimes lead to confusion between Telco personnel and others who use different methods. For instance, radio and TV people are often used to working with wide-band unweighted measurements relative to some zero level. There is a telco term, DBrnC0, which considers a measurement being made at a reference level of zero dBm at some defined point in the system. Other points in a system, such as the other end of a long program loop may not have zero dBm, so that is why the phone company wants to know the signal level relative to the noise power on the line at the point of interest. These measurements are sometimes made with the line terminated by a 500-type instrument, or about 900 ohms, other situations may be with the line terminated by customer equipment, such as an audio amplifier, in which case the measurements are made in bridging mode. Obviously, there is a big difference between measurements made on ordinary subscriber loops, POTS, and program circuits used in broadcasting and other high-quality transmission systems and this instrument tries to accommodate them all.

@ChrisSmith-tc4df 2 ай бұрын

1kHz even would be essentially spot on with the digital telephony 8kHz sampling rate, and that in conjunction with the logarithmic companding would create weird artifacts as the exact same sampling points repeat with an extremely slow drift. Choosing 1004Hz ensures that the sampling points move across the sine wave multiple times per second.

@mnoxman 2 ай бұрын

The count is a timer based thing. It counts noise impulses over a given amount of time (30sec/60sec). Before the days of modems this was a number like 15 impulses per min. good enough for long lines but sucked if you had a modem.